site selection and considerations
Post on 30-Dec-2016
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Site Selection and Considerations Determine your local climate and decide if you need a greenhouse to keep the fish warm or not, see Climates
Effect on System Operation, in the course manual. If your location is warm, but you plan to have a greenhouse for a pest-sensitive crop such as tomatoes, consider getting a bit larger greenhouse to put the fish tanks inside also, as they will benefit from the additional warmth (unless you are in a very sunny and warm location, in which case that is not necessary). If you are going to install a greenhouse on a sloped site, and intend to use the sloped grading method, you will need to tread carefully, as we do NOT YET have an example of a greenhouse for troughs installed on a sloped grading installation. Depending on the greenhouse type, we think it will PROBABLY work well. Just be careful, your building will be at the same angle from level that your finished ground is (doors will open REALLY EASILY one way and with more difficulty the other!).
IMPORTANT: There are now TWO GOOD WAYS to grade your site, based on new information we
developed in the last six months. If your site is flat, you can mostly ignore this section. If your site is sloped, then you WILL need to do some kind of grading to prepare it for the fish tanks and troughs. While the fish tanks need a flat and level area, there are two ways to grade your site for the troughs for a large commercial aquaponics system, the traditional way of grading flat and level terraces with steep short sections between them; and the new way well call sloped grading. Here are descriptions of the two to help you decide whats best for you:
1. Traditional consists of grading terraces on a sloped site for your fish tanks and troughs that are LEVEL
(which is different from FLAT) in both directions, lengthways to the troughs, and sideways to the troughs. This method of grading leaves you with large flat areas that are easy to put your installation on. It also has a couple of potential drawbacks: the first one is that you have relatively steep sloped areas between each flat and level terrace and the next terrace that are not useful for much of anything because of their steep slope, but upon which you DO need to install stairs or other methods of movement and transportation for people and up and down between terraces. The other drawback is that it involves a LOT of grading to turn a sloped piece of land into flat and level terraces. Grading costs money, and grading a sloped site level costs the most money. Sloped grading, which we discuss next, can save you a tremendous amount of money if your site is hard or rocky, or even if it is soft dirt but sloped. We wish we knew about sloped grading almost four years ago when we graded for our farm; we would have done our WHOLE farm this way!!
2. Sloped grading for slant troughs consists of grading your site level in the long direction of the troughs in the areas you will install hydroponics troughs, but grading it FLAT to match the existing slope in the sideways direction of the troughs (flat, NOT LEVEL, in this direction, theyre different!). Yes, now your FLAT trough pad slopes significantly DOWNWARDS from the top trough to the bottom one, but is level in the lengthways direction of the troughs. How do you make your troughs now? You build the uphill side of the trough shorter and the downhill side of the trough taller, so that the trough is still LEVEL across the top of each individual trough, but the BOTTOM of the trough is sloped downhill (the top of the trough CANT slope unless you know a way to make the water in your trough slope). Each sloped trough is installed slightly lower than the previous one uphill from it.
You need to get the average measurement of the slope under the troughs, figure out how much difference that is over the 4 feet 6 inches of trough width, then divide that in half. Add half of this number to the downhill side of the trough and subtract half from the uphill side of the trough. Example: your sloped grading is done, and youve used a builders level to shoot the pad, or a carpenters level taped to a very straight 20-foot 2x6 and measured how far down the end of the 2x6 is off the ground when the other end is ON the ground and the 2x6 is level. However you did it, youve measured that the trough pad slopes downwards 17-3/4 inches in 20 feet of horizontal distance, or 0.8875 per foot. Over the 4-foot 6-inch width of the trough, this is 3.99 of slope. Well round off to 4 to make this easy, and divide by half. That is 2 inches, and we subtract 2 inches from the uphill side of the trough (that would have been 12 tall for a traditional flat terrace), and build ALL our uphill sides 10 high. We ADD 2 to the downhill side of the trough (that also would have been 12), and build ALL our downhill sides 14 tall. You might want to make a test trough from some plywood scraps first to check your math, before you cut all the plywood for a big system and find out there was a mistake.
When you install these, install the uphill side first, then the downhill side by leveling to the uphill side. Everything else works the same way as standard troughs described later in this manual. We installed a test sloped trough on a slope of 3.88 inches per foot (remember, our example was 0.8875 per foot!), and although it was quite odd-looking, it held water and functioned as a trough.
Slant troughs in a sloped grading installation. Note airlines with valves stubbed-out, pipes in VERY shallow trench to left (rocky ground!), Mirafi ground cloth ready to finish installation after trench is backfilled.
Sealing slant troughs to the Mirafi geotextile ground cloth with mortar and a trowel keeps mice, bugs, and dirt out from under your troughs.
Fish tank in foreground, four 75-foot long slant troughs in background.
If your site is dirt, you have more choices about where you want the aquaponics system to go because
it is cheaper to move dirt than rocks. Follow the directions in the construction drawing. Make sure you read the previous bullet if you are dealing with a flat site. If you have a sloped site and decide to use the traditional grading method of terraces with slopes between, AND decide to use a sump tank (optional) the sump tank sits on a small flat pad that is four feet lower than the large pad for the tanks and troughs (you can usually hand-grade the sump tank pad with a pickax and rake). This gives you a gravity flow all the way from the high spot (the rearing tank) to the lowest spot (sump tank). Grade everything within 1" of level length-wise on the troughs. You can put a slight slope in crossways to the troughs, maybe 1" in four feet, so that your system finish ground drains runoff down slope in a rain instead of puddling around and between the troughs. This also makes it easy to get the subsequent troughs in the series working correctly: it's much harder to get water to flow uphill if you accidentally put the next trough two or three inches higher than the last one. Your grading contractor is responsible for getting this right, he should have a level and know how to use it. If he says it is level, then when you go to rake the sand out (covered next), and find your pad is 12 higher on one end than the other, you will wish you checked this before you paid him his final payment.
If your site is dead flat, omit the sump tank, and install your pump connected to the aquaponics trough's
outflow as shown in the CAD drawings.
If your site is rock or otherwise very "hard", you want to carefully site your system to minimize grading costs. Also, read and re-read the previous section on slant grading, and slant troughs, because you can save a lot of money doing it that way. The cost of bringing in fill may be less than the cost of squashing what you have with a D9 until it's flat enough to build a system on. Also, it is very easy to get the fish tank and hydroponics trough areas flat and level. First, have your grading contractor do the best he can with whatever your substrate is.
IMPORTANT! After the grading contractor is finished, dump a few cubic yards of sand (also known as pipe bedding, sometimes a LOT cheaper than sand) on your pad and hand-rake it out with rakes to make your finished level. If you have or can rent an optical level as shown in previous picture, use it first to get the pad as level as possible from end to end. It is easy then to check level in smaller areas (and knock down bumps and fill in holes) if you get a 16-foot 2x4 and duct tape a 6 foot builder's level to the top of it. Use the 2X4 to check level both ways on the pad if you have a pad that is level in both directions; and to check level and flat on the pad if you have a slope-graded pad, as you grade the sand with your rakes. After it is done, run a compactor or a bulldozer over it to compact it (if you have one), then go back and fill in any small areas that have settled with a rake, wheelbarrow full of sand, and your level on the 2X4.
If your site is steep, you may need a larger water pump than specified if you end up with more head
from your sump tank/last trough up to your rearing tank than 6 feet or so.
Grading and Site Preparation
Everybody needs a Siamese survey cat! Tim is laying out the grading with approximate levels. This optical instrument hes using costs about $400 or so and saves tons of time laying out your aquaponics system and buildings. It allows you to double-check and confirm that your grading contractor REALLY got your pads level and flat before you pay him the last payment due. It's also a great tool to use to make sure your drainage slopes drain rather than clog.
IMPORTANT: Get a good, experienced grading contractor. There are lots of people with an old D3, backhoe or skidsteer